Stories fundamentally alters the nature of Snapchat, in three ways: messages now live for up to twenty-four hours, rather than for ten seconds; they can be viewed repeatedly within that window, instead of just once; and they create within Snapchat what is effectively a stream of content and a semi-public persona. While the changes wrought by the twenty-four-hour window appear to be the most drastic, because of how central temporality is to the service, it is, in fact, the latter change that will most dramatically alter the nature of Snapchat.

The Snapchat app is composed of four side-by-side screens that you swipe among. Despite the addition of a major new feature, its exceptionally basic architecture is unchanged. Starting with the left-most screen, they are arranged in this order: your inbox, the camera, your friends list, and a panel to “add friends.” “Stories” lives in the same space as your friends list; while a new section at the top displays the most recent updates, you generally have to scroll through your friends to hunt down every single story. Pressing and holding a friend’s icon plays every clip he has designated as a story over the previous twenty-four hours. At a minimum, a user’s stories can be seen by everybody that he or she deems a friend. They can also be completely public if the user chooses, visible to anyone with an account.

Snapchat has been working on Stories for a year, with about a month of testing, said Evan Spiegel, Snapchat’s twentysomething C.E.O., who in his flagrant youth neatly embodies the popular image of a technology entrepreneur. Despite a general sense of polite self-assurance, the ends of his sentences are often punctuated by nervous giggles. Stories, he explained the other day, were created largely in response to the popularity of “mass snaps,” or sending photo messages to most or all of your friends list simultaneously. “I fucking hate mass snaps,” he said in a quiet, anxious voice, in between bites of a cookie. The problem with mass snaps is that they can be intrusive. Snapchat in its earlier form effectively obligated you to look at a mass snap, no matter how disinterested you were, by taunting you with an unread count, much like e-mail. Spiegel, like many people, is intensely bothered by notifications. (This is partly why, unlike on Twitter or Facebook, you cannot tell if you are someone else’s friend on Snapchat; if a person opts to receive snaps from only their friends, and you are not one of them, the snaps you send him will simply disappear into the ether. He will be blissfully unbothered by your snaps, you’ll eventually notice that your snaps have gone unreciprocated, and the whole matter will quietly smother itself.) Stories is an attempt to off-load those essentially public snaps, sent to an entire friends list, from Snapchat’s infrastructure.

The result, however, is that while you previously opened Snapchat in order to view a message explicitly directed at you—even if you received a mass snap, the sender had to intentionally check the box next to your name—you now have a reason to open it constantly, like Twitter or Facebook: there’s always content waiting. While Spiegel explained that it’s designed specifically so that it can be ignored—and you can simply secretly unfriend somebody—it nonetheless ties Snapchat to the well-worn model of the stream, which it had previously rejected. The psychology is inherently different than the one on which Snapchat was built: in both its ephemerality and structure, the service was largely free of the trappings of the social networks that had come before it.

Just as importantly, Stories can be published (if one allows) so that they’re completely exposed to anyone on Snapchat, creating a de facto public profile. These profiles mutate every twenty-four hours, so that a static, digital profile never accumulates; every day on Snapchat, you effectively become a new person, which Spiegel believes is true in real life as well. But having a public profile, even an amorphous one, turns the insularity of Snapchat inside out. What had been a place to exclusively share the photos you deemed too weird or unattractive or disposable to plaster on Instagram or Facebook for a small eternity is now implicitly asking users to create public content for it, too. By going public, Snapchat risks no longer being the place for the private. As one programmer said in a tweet, “they can’t have it both ways.” While anecdotes are not data, and neither I nor the two dozen people I snap with regularly are among Snapchat’s most hardcore users, I’ve noticed a precipitous drop in Snapchat activity since Stories launched over a week and a half ago. My friends only post a handful of Stories a day, at best, and I’ve received far fewer messages than I used to get. (Spiegel didn’t have any metrics to offer when I met him last week, but said he was happy with the launch so far.)

It would be ironic if Stories spoiled Snapchat for some users, since they were designed, in Spiegel’s telling, to save it. In becoming more public, it would also seem to possibly contradict what he said was the company’s most important value: empathy. When I asked him to give an example of a product designed without empathy, he immediately named Google Glass. It works in the world that Google has constructed for itself, he explained, but in the real world it simply makes most people uncomfortable. The question for Snapchat, as it grows beyond three hundred and fifty million snaps a day, is who it’s going to feel empathy for.

Matt Buchanan was a science and technology editor for newyorker.com from 2013 to 2014.